The use of pipelines to connect vessels and transport material is a common practice in the processing industry,. Often, these pipelines carry potentially hazardous materials, such as flammable gases. The potential of fires and explosions in the process industry bas been well recognized and is addressed in consensus guidelines such as NFPA 68 - Guide for Venting of Deflagrations and NFPA 69 - Explosion Prevention Systems. Both of these gu ides differentiate between vessels and piping systems by providing different rules to address the differences in explosion propagation behavior Both NFPA 68 and NFPA 69 are based on an understanding of explosion propagation behavior developed from empirical or experimental evidence, The purposes of this paper are to present experimental evidence and to further develop a detailed understanding of combustion propagation in industrial scale piping, primarily deflagration propagation in pipes. However, it is also the intent to understand the transition points between fires and deflagrations, and between deflagrations and detonations as related to piping,stems. In order to study combustion propagation in industrial scale piping, three pipe diameters and three fuels were selected. Although, gaseous fuel mixtures are often transported in waste streams, only pure fuels were used in this study, The effect of bends was evaluated but other piping system components were not evaluated.